The present invention relates to a semiconductor device and, more particularly to a technique useful for a driver IC (Integrated Circuit) used in a liquid crystal display (LCD).
An LCD is composed of a plurality of pixels arranged vertically and horizontally, which are units to display pictures and characters. An increase in the number of pixels makes a curved line displayed smoother, resulting in higher definition image. When a color image is displayed, three primary colors red (R), green (G), and blue (B) are combined to constitute one pixel.
An LCD using a thin film transistor (TFT) as a switch for active matrix system, which is a method for driving the pixels, is composed of a glass substrate over which first wires and second wires are arranged in vertical lines and horizontal lines respectively, and the TFTs that serve as the switches are arranged at the intersections of the lines, and a liquid crystal layer, into which a liquid crystal material is sealed, is arranged in the vicinity of each switch. In the LCD, by applying an address signal to the second wire in each line, the TFTs in each line are switched into conductive state and data signals supplied from the first wire are written into the liquid crystal layers (pixels). On the other hand, the TFTs in the line to which the address signal is not applied remain in a non-conductive state and the previously written data remain on hold (stored).
In addition, the driver IC configured to drive the liquid crystal of an LCD (hereinafter, referred to as “LCD driver”) is composed together with semiconductor circuits, such as a driver output circuit, a logic circuit, etc., formed over the main surface of a semiconductor chip (semiconductor substrate). Over the main surface of the semiconductor chip constituting the LCD driver, bumps are provided as external electrodes for, for example, outputting signals from the driver output circuit to the source lines and the gate lines, and pads are also provided under the bumps for forming the bumps. Owing to this arrangement, in order to preserve the bonding strength and the bonding precision, or to meet the specifications required by assembly process of the semiconductor chip, the dimensions of the pad cannot be reduced compared to the reduction in dimensions of the semiconductor circuits, such as a driver output circuit, a logic circuit, etc., and interconnect wires.
In Japanese patent laid-open No. 2004-95577 (patent document 1), a technique is disclosed, which makes the height of a plurality of pads uniform by uniformly flattening the surface under the pads which are placed over the region of the semiconductor circuit and the interconnect wires over the main surface of the semiconductor chip.
Further, in Japanese patent laid-open No. 2002-246470 (patent document 2), a technique is disclosed, which provides a protective element between the connection of a pad and a semiconductor circuit (for example, a driver output circuit) in order to prevent an electrostatic breakdown in the semiconductor circuit in an LCD driver.